Dual band stripline antenna

ABSTRACT

A dual band antenna is disclosed in which the radiating elements for each band are slots in a conductive sheet and in which the slots are fed by wave guides and stripline distribution means. The conductive sheet is an outside layer of a sandwich comprising two outside conductive layers and two sheets of dielectric between said outside layers and said stripline distribution means or transmission line, between the dielectric sheets. Two additional similar sandwiches are used having therein transmission lines and couplings thereto for the two waves to be radiated. The outside layer of a middle sandwich is in close contact with an outside layer of the two other sandwiches, whereby there is no radiation from between the sandwiches. To make this close contact possible, the sandwiches are made with flat smooth outside surfaces and the sandwiches are not held together in a manner that may cause a bumpy surface.

United States Patent Shelton [54] DUAL BAND STRIPLINE ANTENNA [72] Inventor: Philip L. Shelton, Scottsdale, Ariz. [73] Assignee: Motorola, Inc., 2, Franklin Park, Ill.

[22] Filed: Dec. 11, 1970 [21] Appl. No.: 97,147

[52] US. Cl. ..343/77l, 333/84 M [51] Int. Cl. ..H0lq 13/10 [58] Field of Search ..343/767, 771; 333/84 M [56] References Cited UNITED STATES PATENTS 2,877,427 3/1959 Butler ..343/770 3,044,066 7/1962 Butler ..343/77l 3,569,973 3/1971 Brumbaugh ..343/77l 3,587,110 6/1971 Woodward ..343/8l4 Primary Examiner-Eli Lieberman Attorney-Mueller and .Aichele [451 Sept. 12,1972

[57] ABSTRACT A dual band antenna is disclosed in which the radiating elements for each band are slots in a conductive sheet and in which the slots are fed by wave guides and stripline distribution means. The conductive sheet is an outside layer of a sandwich comprising two outside conductive layers and two sheets of dielectric between said outside layers and said stripline distribw tion means or transmission line, between the dielectric sheets. Two additional similar sandwiches are used having therein transmission lines and couplings thereto for the two waves to be radiated. The outside layer of a middle sandwich is in close contact with an outside layer of the two other sandwiches, whereby there is no radiation from between the sandwiches. To make this close contact possible, the sandwiches are made with flat smooth outside surfaces and the sandwiches are not held together in a manner that may cause a bumpy surface.

5 Claims, 5 Drawing Figures PATENTEDSEPIZ m2 3,691,563 sum 1 or 2 INVENTOR. Phi/1p L. She/fan WW f Arrys.

PATENTED SEP 12 m2 SHEET 2 [1F 2 INVENTOR. Phil/10L. She/fan WM M Arrrs.

DUAL BAND STRIPLINE ANTENNA BACKGROUND It is often necessary in radio direction finding operation to transmit waves in two different wave bands into the same space and often in the same direction. While prior art devices for so radiating waves in different bands are known, they are often large, bulky devices using high frequency plumbing for the energization thereof, which are difficult and expensive to make.

It is an object of this invention to provide an improved dual radio wave radiating device.

It is an object of this invention to provide a dual radio wave radiating device that can be made to a great extent by printed circuit techniques.

SUMMARY According to the invention, a structure comprising three sandwiches in close electrical contact are provided. Each sandwich includes two outside layers of a conductive material such as copper and two intermediate sheets of insulating material between the outside layers and a middle layer comprising a transmission line of the stripline type which is used as an energy distribution means. The top or first layer has a plurality of parallelly arranged slots cut therethrough to act as radiator elements for waves of one frequency band, and another plurality of parallelly arranged slots cut therethrough to act as radiator elements for the waves of another frequency band. The first plurality slots may all be of the same size but different in size from the slots of the second plurality thereof, and the slots of the two pluralities thereof may be arranged perpendicularly to each other. The first plurality of slots may be continuations of holes through the two dielectric sheets and through the other outside sheet, the insides of the holes having conductive material deposited thereon and electrically connected to the two outside layers to produce wave guides. The other plurality of slots extend only through the outside layer and the intermediate layer of the top sandwich acts only as a stripline feed means or distribution or transmission line for the slots of the other plurality thereof. The conductive top layer of the middle or second sandwich has slots in position to register with the wave guide through the top sandwich. The center layer of a middle sandwich is a stripline transmission line for feeding the slots in the top layer thereof. Wave guides also extend through the middle sandwich and are positioned to feed the stripline middle layer of the top sandwich. The top layer of the bottom sandwich has slots therein positioned to register with the wave guides through the middle sandwich and the center layer of the bottom sandwich is a stripline transmission line to feed the wave guides through the center layer. A hole is provided through the bottom layer for connection to the outside layer of the middle sandwich of means to feed the center layer of the middle sandwich. The transmission line in the bottom sandwich is fed by a wave guide coupled through a hole in the bottom layer of the bottom sandwich to the transmission line in the bottom sandwich. Each of the sandwiches has smooth, level outside layers which are to be in contact whereby upon contact to the three sandwiches, they are in good electrical contact, whereby radiant wave energy cannot leak out from between the several sandwiches. This good electrical contact is provided by fastening the several layers of the sandwiches together in a manner which does not provide bumps or irregularities on the surface of the sandwiches as if the sandwiches were affixed together by rivets. The several layers of the sandwiches are therefore glued or otherwise bonded together and the insides of the holes through the sandwiches have conductive material plated thereon. Since the conductive parts of the several sandwiches can be made by printed circuit techniques, and since the holes in the several sheets of dielectrics are straight through and of simple shape, the disclosed dual band antenna can be made quite economically in single or large quantities.

DESCRIPTION The invention will be better understood upon read ing the following description in connection with the accompanying drawing in which:

FIG. 1 is a plan view of the antenna embodying this invention,

FIG. 2 is a section of FIG. I on line 2--2 thereof,

FIG. 3 is a section of FIG. 1 on line 3-3 thereof,

FIG. 4 is a fragmentary view of the transmission line of the top sandwich showing the positions of the several slots in the top conductive layer in dotted lines for ex planatory purposes, and

FIG. 5 is a fragmentary view of the transmission line of the middle sandwich and also showing the relative positions of the several slots to the transmission line in dotted lines.

Turning first to FIGS. 1 and 2, a top sandwich 10, a middle sandwich 12 and a bottom sandwich 14 are shown. The top sandwich 10 comprises a top conductive layer 16 and a bottom conductive layer 18. The top layer 16 has a plurality of slots 20 formed therein. While 16 slots 20 are shown, there may be as many thereof as is desired. While all of the slots 20 are shown as being parallel and arranged along equidistant lines, the slots 20 may be arranged as is desired. A second plurality of slots 22 are also formed through the layer 16, the slots 22 being smaller than the slots 20 and being arranged between and perpendicular to the slots 20. Again the number and positions of the slots 22 may be as desired.

The sandwich 10 also comprises two sheets 24 and 26 of dielectric material between the layers 16 and 18. Holes 28 of the same size and shape as the slots 20 extend through the two sheets 24 and 26 and register with the slots 20. A stripline transmission line 30 is positioned between the layers 24 and 26. The bottom layer 18 has slots cut therethrough registering with the holes 28. The insides of the holes 28 are plated in a known manner with a conductive material, this conductive material being electrically connected to the layers 16 and 18, whereby the holes 28 act as wave guides for leading energy to be radiated to the radiating slots 20 as will be further explained. The transmission line 30 is arranged in such manner that it is insulated from the wave guides 28. A plurality of holes 32, only one of which is shown in FIG. 2, is provided in the bottom layer 18 for purposes to be described. The layer and sheet 16 and 24, the stripline 30*, and the layer and sheet 26 and 18 are fixed together as by gluing or otherwise bonding, the stripline 30 being so thin that it does not interfere with this fixing together, whereby the outside layers of the sandwich are quite level and smooth.

The middle sandwich 12 comprises an upper and a lower conductive layer 34 and 36. The upper layer 34 has slots 38 therein registering with the wave guides 28 but of a smaller area than the wave guides 28. A wave guide 40, made like the wave guide 28, extends through the layers 34 and 36 and through the intermediate dielectric sheets 42 and 44 and registers with a hole 32. While only one wave guide 40 is shown in FIG. 2, there may be as many thereof as there are holes 32. A transmission line 46 extends between dielectric sheets 42 and 44. The transmission line 46 is insulated from the wave guide 40. A hole 48 is provided in the bottom layer 36 so that the interconductor 50 of a coaxial line 64 may extend through the hole 48 and be insulated from the layer 36 and be connected to the transmission line 46. The layer 12 is made like the layer and has smooth and level outside surfaces.

The bottom sandwich 14 has an upper and a lower conductive layer 52 and 54. The layer 52 has a relatively large hole 56 therethrough which is concentric with the hole 48, and as many holes 58 as there are wave guides 40, the holes 32 and 58 being somewhat smaller in area than the wave guides 40 and registering therewith. The hole 56 continues through the intermediate dielectric sheets 60 and 62 and the bottom layer 54 and the coaxial cable 64 extends into the hole 56. The outside conductor of the coaxial cable is conductively connected to the layer 36, and the inner-connector of the coaxial cable 64 is connected to the conductor 50. A transmission line 66 is positioned between the sheets 60 and 62. A hole 68 is provided in the bottom layer 54 and a wave guide 70 is conductively fixed to the layer 54 around the hole 68.

In operation, radiant energy which is to be radiated by the slots is applied by way of the coaxial conductor 64 and the inter-conductor 50 to the transmission line 46 which supplies energy to the wave guides 28 by way of the holes 38 by radiation, in effect, across the dielectric sheet 42. The way that this is accomplished may be understood upon observing FIG. 5. The transmission line 46 has portions which extend across the wave guide 28, the dotted lines in FIG. 5 representing the position of the wave guides 28. The transmission line 46 is connected to the pin 50, the length of the transmission line from the pin 50 to the several wave guides 28 being such as to provide energy at the desired phase relation to the several wave guides 28 and therefore to the several slots 20 for radiation therefrom in a pattern in a known manner. As is seen in FIG. 5, the connections comprising the configuration whereby the transmission line 46 will not interfere with other elements of the middle sandwich 12, such as the wave guides 40, is due to the fact that the transmission line 46 may be shaped in any convenient manner.

The slots 22 are fed by energy supplied through the wave guides 70. This energy is radiated across the dielectric 62 to the transmission line 66. The energy in line 66 is radiated across the dielectric 60 to the wave guide or guides 40 through the holes 58, only one of each being shown. The energy from the wave guide 40 is radiated to the transmission line 30 through the hole 32 and the energy in the transmission line 30 is radiated to the slots 22. Attention is called to FIG. 4 in which a part of the transmission line 30 is shown in relation to the holes 32 and the slots 20 and 22, the position of the latter being shown in dotted lines in FIG. 4. Again, the

connections can be routed to avoid obstacles such as the wave guides 28 in constructing the transmission line 30.

No energy that is fed to the coaxial line 64 or to the wave guide leaks out between the sandwiches l0, l2 and 14, since the layers 18, 34, 36 and 52 are made very smooth and level whereby the contact between these layers is a good electrical contact. While the coaxial line 64 and wave guide 70 feeds are shown, whatever feeds that are convenient may be used. The positioning and size and shape of the slots 20 and 22 may be what is convenient for the wave bands to be radiated in desired patterns.

While both groups of radiating slots 20 and 22 and their feed means are shown and described, it will be clear that only one group of slots 20 or 22 and the feed means therefor need be provided, or, if both groups of slots and their feed means are provided, only one group of slots may be energized, whereby only one group of slots will radiate. Furthermore, the radiations from the two groups of slots are independent of each other.

What is claimed is:

l. A dual antenna comprising:

a plurality of sandwiches, each sandwich including two conducting layers, two dielectric sheets between said conducting layers, and a transmission line between each two dielectric sheets,

the outer surface of at least one of said conducting layers being smooth and level,

means for holding said sandwiches together with said smooth layers in contact,

means for applying radiatable energy to one of said sandwiches,

means to so couple said sandwiches that said energy arrives through said contacting layers to another of said sandwiches, whereby due to the contact of said smooth layers, energy is not radiated out from between said sandwiches,

one of the two conducting layers of said another sandwich is an outer conductive layer having two pluralities of holes therethrough,

one of said plurality of holes being the ends of respective wave guides through said another sandwich and energized by said transmission line in said one sandwich, and

said other plurality of holes being energized by the transmission lines in said another sandwich.

2. The dual antenna of claim 1 in which one of the conducting layers of said one sandwich is an outer conductive layer and said one sandwich includes at least one wave guide therethrough for energizing said transmission line in said other sandwich, and

means to apply energy to at least one wave guide and to said transmission line in said one sandwich.

3. The dual antenna of claim 2 in which said means to apply energy comprises a third sandwich having outer layers of conductive material, one layer thereof being smooth and level and being held against said one sandwich,

said third sandwich includes two dielectric sheets and a third transmission line between said last mentioned dielectric sheets,

wave guide means for applying energy to said third transmission line through a hole in the outer conductive layer of said third sandwich, and

coaxial means for applying energy to the transmistively connected to the transmission line in said sion line of said one sandwich through said third one sandwich.

sandwich. 4. The dual antenna of claim 3 in which the outer conductor of said coaxial line is connected to aconduc- 5 tot wave conneFted the outer five layer of said one Sandwich, and ductive layer of said third sandwich.

the inner conductor of said coaxial line is conduc- 5. The dual antenna of claim 4 in which the conduc- 

1. A dual antenna comprising: a plurality of sandwiches, each sandwich including two conducting layers, two dielectric sheets between said conducting layers, and a transmission line between each two dielectric sheets, the outer surface of at least one of said conducting layers being smooth and level, means for holding said sandwiches together with said smooth layers in contact, means for applying radiatable energy to one of said sandwiches, means to so couple said sandwiches that said energy arrives through said contacting layers to another of said sandwiches, whereby due to the contact of said smooth layers, energy is not radiated out from between said sandwiches, one of the two conducting layers of said another sandwich is an outer conductive layer having two pluralities of holes therethrough, one of said plurality of holes being the ends of respective wave guides through said another sandwich and energized by said transmission line in said one sandwich, and said other plurality of holes being energized by the transmission lines in said another sandwich.
 2. The dual antenna of claim 1 in which one of the conducting layers of said one sandwich is an outer conductive layer and said one sandwich includes at least one wave guide therethrough for energizing said transmission line in said other sandwich, and means to apply energy to at least one wave guide and to said transmission line in said one sandwich.
 3. The dual antenna of claim 2 in which said means to apply energy comprises a third sandwich having outer layers of conductive material, one layer thereof being smooth and level and being held against said one sandwich, said third sandwich includes two dielectric sheets and a third transmission line between said last mentioned dielectric sheets, wave guide means for applying energy to said third transmission line through a hole in the outer conductive layer of said third sandwich, and coaxial means for applying energy to the transmission line of said one sandwich through said third sandwich.
 4. The dual antenna of claim 3 in which the outer conductor of said coaxial line is connected to a conductive layer of said one sandwich, and the inner conductor of said coaxial line is conductively connected to the transmission line in said one sandwich.
 5. The dual antenna of claim 4 in which the conductor of said wave guide is connected to the outer conductive layer of said third sandwich. 